1. - A subscriber served by switch A wants to reach a service provided by lines starting with 800 (e.g. reserve a rental car) - The subscriber dials the company's advertised 800 number - When the subscriber has finished dialing, switch A recognizes that this is an 800 call and that it requires assistance to handle it properly - Switch A formulates an 800 query message including the calling and called number and forwards it to either of its STPs (e.g., X) over its A link to that STP (AX) - STP X determines that the received query is an 800 query and selects a database suitable to respond to the query (e.g., M) - STP X forwards the query to SCP M over the appropriate A link (MX)

2. - SCP M receives the query, extracts the passed information and (based on its stored records) selects either a real telephone number or a network (or both) to which the call should be routed - SCP M formulates a response message with the information necessary to properly process the call, addresses it to switch A, picks an STP and an A link to use (e.g., MW), and routes the response - STP W receives the response message, recognizes that it is addressed to switch A, and routes it to A over AW - Switch A receives the response and uses the information to determine where the call should be routed - Switch A then picks a trunk to that destination, generates an initial address message (IAM) and proceeds (as it did in the previous example) to set up the call.